import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 98152
 * Date: 2024-11-11
 * Time: 23:59
 */
public class Test3 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        in.nextLine();
        String str = in.nextLine();
        int len = str.length();
        //1.找出字符串中数量最多的字母及其数量
        int maxCount = 0;
        String str1 = str.substring(0,1);
        for(int i = 0; i < len; i++) {
            str1 = str.substring(i,i+1);
            int count = 1;
            for(int j = i+1; j < len; j++) {
                String str2 = str.substring(j, j+1);
                if(str1.equals(str2)) {
                    count++;
                }
            }
            if(maxCount < count) {
                maxCount = count;
            }
        }
        //System.out.println(maxCount);
        //System.out.println(str1);

        //2.以数量最多的字母拆分字符串,并将拆分出来的组合起来
        StringBuffer stringbuffer = new StringBuffer();
        String[] string = str.split(str1);
        for(String s : string) {
            stringbuffer.append(s);
        }
        //System.out.println(stringbuffer.toString());

        //3.将数量最多的字母插入组合中
        for(int i = 1; maxCount > 0 && i <= stringbuffer.length(); i += 2) {
            stringbuffer.insert(i, str1);
            maxCount--;
        }

        //4.判断
        if(maxCount <= 2) {
            if(maxCount == 1) {
                stringbuffer.insert(0, str1);
            }
            if(maxCount == 2) {
                stringbuffer.insert(0, str1);
                stringbuffer.insert(string.length, str1);
            }
            System.out.println("yes");
            System.out.println(stringbuffer.toString());
        }else {
            System.out.println("no");
        }
    }
}
